I am finally glad to see that you acknowledge that no graded response can be
replicated exactly, I was not sure if you believed this. I still however,
disagree with your closing statement
> The fact is that real neurons in real nervous systems DO process
> information in an analog manner using graded responses. Like it
> or not, that is how the cells work.
You cannot just make a statement or believe in something and not think about
the consequences - a scientist must always do this. It is not a question of
liking it or not, but rather keeping one's mind open to all possibilities.
It is now prudent to change the format of the discussion slightly, in the
following way. For the conscious human brain to process information in an
analogue manner, it would imply that it is able to do this without having to
'worry' about the exact properties of each graded reponse. Indeed, the brain
would probably use some statitistical tools to smooth out the
inconsistencies caused by graded responses occurring in succession. I
suppose that is where the heart of the matter lies - if you believe the
brain works in a statistical manner to process information, then so be it,
it can do so using analogue neurons. Unfortunately, you have still not given
the factor(s) that would make a neuron analogue. Furthermore, when dealing
with neuronal networks, more inconsistencies would arise, requiring a
further degree of 'smoothing out'.
There is of course, one way to get around all this statistical requirement
and that is to suggest that the brain can process information using each and
every graded response as it happens to produce the coherent image of the
self. How it could do this, would most likely be incomprehensible and
completely unknown. And there is the difference between you and I, you would
have to believe either of the two conclusions drawn upon by insisting on an
analogue brain, whereas I doubt them.
> But anyone who has actually looked at action potentials recorded from real
> cells knows that they are not all identical -- some are larger some
smaller,
> -- some have faster rise and fall times, some slower -- some have longer
> duration, some shorter. And these variations are found between cells and
> within one cell from moment to moment depending on the history of activity
> and on signals delivered from adjacent cells, not to mention the glial
> activity.
This is of course true, and would only produce the same two conclusions
already mentioned. But you are missing the point, the generation of AP, or
rather the AP itself as a physical event would affect in some manner or form
whatever it happened to make final contact with. And here is the important
point, it would inevitably effect the state of whatever it finished upon -
another neuron - in ways that may still not be known, simply because
laboratory conditions differ markedly from the real deal (the in vitro to in
vivo extrapolation dilemma) and we may therefore be missing an important
part of the picture. Indeed, here is another place where you and I differ,
the possibility that somehow frequency coding departs from the unknown
analogue state of a single neuron and simply provides an alternative and
controllable solution to the problem. It is because we are unfamiliar and
lack knowledge about such a system that we do not accept it as a viable
solution and therefore fail to truly understand what it implies or to even
comtemplate its role in life. Have you ever wondered why a neuron would fire
in the first place? What makes a neuron do that? Forget the physiology
aspect, but look at it in a philosophical manner. You may be surprised with
what you come up with.
Nobody, not you or I, knows the answer to the original question, all we can
do is speculate, and always keep an open mind. However, as scientists, we
can still aim to eliminate certain answers on the basis of structured logic.
Even then, until the problem is fully understood, many will still disagree.
Richard P Feynmann, one of the greatest physicists/scientists to have ever
lived believed that of all the values of science, 'the greatest must be the
freedom to doubt'. So long as there are ideas, answers may eventually come
forth.
T.L.S.
PS. I shall not be able to write to this newsgroup for another two weeks, so
do not fret if your message goes unanswered.
'The road to absolute truth is long and unknown' and 'Scientists may
sometimes need shovels'
Richard Norman <rsnorman at mediaone.net> wrote in message
news:bWUr5.13814$_e4.591145 at typhoon.mw.mediaone.net...
> I am afraid your postscript says it all
>> "For those who believe,
> no explanation is necessary.
> For those who do not,
> none will suffice."
>> The most interesting thing about physiological systems is how variable
> they are. You generally can NOT replicate exactly a situation which is
> determined by a large number of parameters. But that is a simple fact
> of life. And by having a large number of molecular events, like ion
> channels,
> all responding to the same situation, you do get a significant degree of
> "precision" or repeatability in the response. It is true that the action
> potential is one mechanism that cells have of reducing the variability.
>> But anyone who has actually looked at action potentials recorded from real
> cells knows that they are not all identical -- some are larger some
smaller,
> -- some have faster rise and fall times, some slower -- some have longer
> duration, some shorter. And these variations are found between cells and
> within one cell from moment to moment depending on the history of activity
> and on signals delivered from adjacent cells, not to mention the glial
> activity. And these variations do have important consequences in
> information
> processing in that they significantly influence the amount of synaptic
> transmitter released.
>> You reiterate "I have been trying to put the idea across
> that a neuron cannot process information in an analogue manner
> USING graded responses. This is because of the randomness
> produced during each graded response cannot be replicated
> when needed"
>> The fact is that real neurons in real nervous systems DO process
> information in an analog manner using graded responses. Like it
> or not, that is how the cells work.
>> "Theophilus Samuels" <theophilus.samuels at btinternet.com> wrote in message
> news:8oorj9$8im$1 at plutonium.btinternet.com...> > I feel that you do not understand the real problem at hand. I am now
going
> > to
> > try my best to explain it to you and hopefully you'll then understand.
> >
> > You wrote
> > > Your argument from the beginning seem predicated on your thinking that
> > > a digital system is well-defined whereas an analogue system is
'random'
> >
> > Now read carefully what follows. I am tired of giving examples for
> > how
> > to make a neuron analogue (see earlier postings) - can you think of one?
> No
> > one
> > has yet given a suitable candidate(s). Remember, the states of the
> > continuously variable
> > quantity that you choose should be easily reproducible - for example, if
> you
> > choose the total number of ions taking part in a graded response, which
in
> > turn
> > produces a 'specific state' in the neuron, then do you honestly believe
> that
> > the exact
> > same number of ions can take part in a future graded response to produce
> the
> > same 'specific state' when called for? [See my last posting on the
> workings
> > of an
> > analogue system, the snipped parts].
> >
> > The important thing to remember is that a neuron is unbelievably dynamic
> > with
> > respect to ion concentration, membrane permeability, protein synthesis,
> > protein
> > transport etc. So much so, that one state at a single point in time may
> > never be
> > reproduced in its remaining lifetime! In conclusion, how can information
> > processing in the conscious human brain rely on a system that most
likely,
> > produces unique conditions that exist only once, momentarily in time?
> >
> > Going back to your quote, it is blatently obvious that you have no idea
> > about
> > the suggestions that I have been making, if this is my fault then excuse
> me.
> > When I am talking about a digital system and that the input/output
> mechanism
> > is
> > well-defined, I am talking about AP generation. Anybody knows that an AP
> is
> > an
> > all-or-nothing response - it either happens or it doesn't - to quote
once
> > more 'there
> > is no messing around'. In this sense, a neuron has the means to create a
> > well-defined communication network, so that the AP are generated when
> needed
> > for
> > cross-talk and information processing. I think we need to get away from
> the
> > idea
> > that a single neuron can process information on its own, instead we
should
> > now
> > begin to focus on neuronal networks within the brain, whether they are
> small
> > or
> > large. At this level, the well-defined level with respect to AP, a
> coherency
> > is
> > observed that can never be seen in an analogue neuron. And yes, AP
> > generation is
> > in binary form, but what is the main difference between this binary
state
> > and
> > that found in computers? Time, of course - the frequency coding concept,
> the
> > way these ON and OFF events are able to be produced in trains of action
> > potentials with differing time intervals between each AP. And remember,
> the
> > information contained within these 'constructs' could equally be found,
> not
> > only
> > in the AP itself, but also in the time between AP, i.e. both ON and OFF
> > events.
> > You can now see that the amount of information that can be contained
> within
> > a
> > system like this is almost limitless, but unlike an analogue neuron,
> easily
> > reproducible when needed. The problem we as scientists face, is the
> > inability to intrepret
> > these signals - indeed, we are still unable to track these constructs in
> the
> > smallest neuronal network in situ, let alone be able to understand them.
> > There is never any discrepancy, either the
> > neuron produces the AP or it doesn't, and therein lies the key to how
this
> > system works, a neuron does not generate an AP but waits until it's
forced
> > to or
> > has to (how this is achieved is a big mystery - I don't mean the
> > biophysics -
> > but the actual reason behind its generation).
> >
> > Fortunately, evidence supporting information processing in this manner
> > comes from the use of drugs. In depression, or other neuro
> > conditions, drugs act to suppress or disrupt AP generation by many
> different
> > molecular
> > mechanisms. Susan Greenfield gives a vivid explanation in her latest
book,
> > about
> > how these drugs suppress neuronal communication, and thus influence the
> > emotional and/or conscious state of the individual. Albeit, these drugs
> may
> > work
> > on the molecular scale, but again, the argument I present suggests that
no
> > coherent pattern of graded responses could be reproduced when needed,
and
> in
> > fact, the introduction of exogenous drugs that disrupt the molecular ebb
> and
> > flow would only increase the apparent randomness of the analogue neuron.
> >
> > The original argument way way back, was that the brain processed
> information
> > only in an analogue manner. This was then redefined to include binary
> > processing
> > on a larger scale, so that an analogue/binary system was developed.
> However,
> > by
> > using my argument, I suggest that the brain was never a true analogue
> system
> > in
> > the first place because no one has yet given a suitable candidate for
the
> > physical
> > variable required for an analogue neuron. Instead, if you think about
it,
> > the
> > variable that I have introduced is TIME, so in that case, my proposed
> > continously variable physical quantity was the fourth dimension. Indeed,
> > using this
> > concept one could say the brain processes information in a
> > psuedoanalogue-binary
> > manner (is time physical? -hence pseudo). Whether this gives rise to the
> > conscious human brain is always in
> > question, nevertheless it removes the unimaginable complexity faced with
> > when
> > dealing with analogue neurons.
> >
> > T.L.S.
> >
> > For those who believe,
> > no explanation is necessary.
> > For those who do not,
> > none will suffice.
> >
> >
> > Richard Norman <rsnorman at mediaone.net> wrote in message
> > news:Ecdr5.11798$_e4.468005 at typhoon.mw.mediaone.net...> > >
> > > "Theophilus Samuels" <theophilus.samuels at btinternet.com> wrote in
> message
> > > news:8ojiam$3cq$1 at plutonium.btinternet.com...> > > >
> > > >.....<snip a lot of stuff> The key thing to
> > > > remember here, is that the digitial input/output mechanism is a
> > > well-defined
> > > > operation - it either happens or it dosen't, there's no messing
around
> > [I
> > > > will come back to this again later>
> > > > .....<snip another lot of stuff > Now here
> > > > lies the difference between the randomness of an analogue system
based
> > on
> > > > graded responses (this was the original argument) and .... <snip a
lot
> > > more>
> > >
> > > Your argument from the beginning seems predicated on your thinking
that
> > > a digital system is well-defined whereas an analog system is "random".
> > You
> > > have included this type of statement now in several of your posts.
> > >
> > > This is non only non-sensical, it departs from everything we have
> learned
> > > about the universe in the history of science. There is underlying
> reason
> > > why
> > > a graded or analog system cannot be determinate. The mathematics of
> > > partial differential equations well describes a tremendous variety of
> > > phenomena that are continuously variable in space and in time. In my
> > > mind, digital systems with probabilistic state transitions are far
more
> > > "random" than the clockwork machinery of the Newtonian universe.
> > >
> > >
> > >
> >
> >
>>